Update xls diff script (rewrote in js instead of vbs)

Update xls diff script (rewrote in js instead of vbs)

Patch from Hiroki NAJIMA:
http://tortoisesvn.tigris.org/ds/viewMessage.do?dsForumId=4061&dsMessageId=30489
86

The changelog is here.

 - BUG: Unable to mark difference when "A1" cell is a "Format as Table"'s
header.
 - BUG: Unable handle protected Excel workbooks and worksheets.
 - BUG: Unable handle hidden worksheets.
 - CHG: Rewrote in JScript.
 - NEW: Add performance improvement mode (fast mode). (Default: off)
        It compare directly to opposite worksheets.
        This mode require opened base document at the same time.
 - NEW: Normal mode fallbacks to fast mode when "new" document's structure is
protected.
 - NEW: Open workbooks with Readonly mode to avoid unwilling saving.
 - NEW: Unhide hidden worksheets.
 - NEW: Set tab color if the worksheet was hidden then green, otherwise default.
 - NEW: Activate first worksheet.
 - NEW: Mark workbooks as "saved" to suppress save dialog if nothing changed.
 - NEW: Show warnings which occurred while processing.
 - CHG: Lots of refactoring.

Based on TortoiseSVN revision 23915, 23916

Signed-off-by: Sup Yut Sum <ch3cooli@gmail.com>